It took just seven days before Martin Place gunman Man Monis came to the attention of Australia's intelligence agencies after he lied his way into the country in 1996.

Three years later ASIO deemed the Iranian-born asylum seeker a risk to Australia's national security. And in the week before he took 18 people hostage in the middle of Sydney's CBD last December, the national security hotline received 18 complaints about postings the 50-year-old self-described cleric had made online.

However, a joint report by the federal and NSW governments, released on Sunday, found there were no major failings of intelligence or process in the lead-up to the Martin Place siege, in which Monis and two of his hostages, barrister Katrina Dawson and cafe manager Tori Johnson, died.

Prime Minister Tony Abbott said instead the report gave the "inescapable conclusion" that the system as a whole let the community down.

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Lindt cafe gunman Man Haron Monis, pictured in 2010 - four years before the siege, was praised by the Islamic State publication Rumiyah.

Photo: Kate Geraghty

Mr Abbott said that each time Monis came to the attention of authorities during his 18 years in Australia he was given the benefit of the doubt but that each individual decision was reasonable.

"The cumulative effect of the benefit of the doubt being given to him time and time again is that he was able to wreak havoc on our community," he said. "Plainly, this monster should not have been in our community."

Mr Abbott will on Monday deliver the Commonwealth's response to the report as part of his national security address. He indicated on Sunday it would address issues around immigration and national security and examine if the system leans too much towards favouring the rights of individuals opposed to the broader interests of society as a whole.

NSW Premier Mike Baird said his government would crack down on illegal guns, with the sawn-off pump action shotgun used by Monis in the siege believed to have entered Australia legally but then fallen onto the "grey market" when not returned in the 1996 gun "buy back".

Mr Baird said he would also further strengthen bail laws, compelling judges and magistrates to refuse bail if an accused person is an identified terrorist risk or linked to violent extremism.

This is despite the joint-government reporting finding that there was no indication Monis had a "desire or intent to commit politically motivated violence" prior to the siege.

Instead, the 80-page report gives an insight into a man whose erratic and at times criminal behaviour saw him consistently on the radar of police and national security agencies.

He was assessed as recently as December 2014, the month of the siege, but was found to have fallen "outside the threshold to be included in the 400 highest priority counter-terrorism investigations".

The report found that Monis may not have even been allowed into Australia in October 1996 if proper checks had been carried out.

Known then as Mohammad Hassan Manteghi, he claimed in his visa application to be a lawyer with an Iranian engineering company here to meet BHP Billiton.

That was a lie, and the joint government report found that if Immigration staff had checked the claims his visa might have been refused.

On his arrival at Sydney Airport on October 28, Monis stated his occupation as "doing business" and when questioned about what that involved he replied "carpets".

The report said Customs did not have access to visa applications at that time and, even now that they do, the discrepancy still might not have been picked up if he entered Australia today.

On November 4, seven days after arriving in Australia, ASIO received "potentially adverse intelligence" about Monis. It did not relate to a terrorist threat, but Monis was placed on a movement alert list.

In January 1999, a security assessment by ASIO determined that Monis's continued presence in Australia posed an indirect, and possibly a direct, risk to national security and that he should not be issued a protection visa.

But when investigated again in July 2000 Monis was found not to be a threat and was granted a protection visa.

Monis then changed his name to Michael Hayson Mavros, put away his "religious garb" and applied to become an Australian citizen - a process that took four years but was eventually approved after lengthy security assessments.

The report found that Monis would likely be granted a visa and citizenship today if he presented in the same way he did at that time.

After having not left Australia since his arrival he then made 21 overseas trips between 2003 and 2007, including 10 to Bangkok and some journeys lasting only a day. Why he undertook these trips no one knows.

At the end of 2006 Michael Hayson Mavros becomes Man Haron Monis, claiming he wanted to become more readily identifiable as a Muslim and to educate youth away from terrorism.

Monis offered to become a source for ASIO - but the spy agency was concerned about his unusual behaviour.

Monis then began a letter-writing campaign sending letters, faxes and media releases to high profile politicians, the Queen, the Pope and a DVD to a US news network with a purported fatwa against President Barack Obama.

He came to the attention of the NSW Joint Counter-Terrorism Team and at the end of 2009 he was charged for sending offensive letters to families of Australian soldiers killed in Afghanistan.

During this time Monis also worked as a "spiritual healer" and was alleged to have sexually assaulted several clients.

He was convicted of stalking his ex-partner and in December 2013 was charged with being an accessory to her murder. He was granted bail. Four months later he was charged with sexual assault offences committed as a spiritual healer and was again released on bail.

The joint government report said consideration was given by the Office of the Director of Public Prosecutions and police to challenge that decision, but given the circumstances of both cases and the bail laws in place at the time it was deemed any appeal would be unsuccessful.

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Monis was again placed on law agencies' radar in December 2014 when the National Security Hotline received 18 calls and emails about his Facebook page.

The NSW Police and AFP found the Facebook posts contained no indications of harm of an imminent threat on December 12 and closed their investigations - three days before the Martin Place siege.